As shown in FIG. 1, a ceramic honeycomb structure 100 of this type is formed by bundling a plurality of porous honeycomb segments 2 through adhesive layers 3, where the porous honeycomb segments 2 are provided with numerous circulation holes 4 partitioned by partition walls and penetrated in an axial direction.
Document 1: Japanese Unexamined Patent Publication No. 2000-7455
Specifically, the ceramic honeycomb structure 100 is formed by mutually bonding sixteen pieces of the porous honeycomb segments 2 each in a quadratic prism shape into a four-by-four matrix through the adhesive layers 3.
Bonding at this time is performed by interposing the adhesive layer 3 between adhered surfaces 2a and 2a of the porous honeycomb segments 2 and 2, and then giving vibration to the honeycomb segments 2 and 2 while applying a pressing force thereto.
Specifically, in the bonding process, as shown in FIGS. 2A to 2E, a first porous honeycomb segment 2 in which a foundation layer is formed on an adhered surface 2a is firstly placed on the lowermost portion of a notched portion 51 of a supporting jig 50. Next, a second porous honeycomb segment 2, in which a foundation layer is formed on one adhered surface 2a and an adhesive is further coated on the foundation layer, is disposed closely to the first honeycomb segment 2 so as to allow the adhered surfaces 2a to face each other while interposing the adhesive therebetween (see FIG. 2A) . In this state, end surfaces of the two honeycomb segments 2 and 2 are pressed with a pressing plate (not shown) and are positioned in advance. Further, a pressing jig 52 is allowed to abut on the latter honeycomb segment 2 so as to press the honeycomb segment 2 in a vertical direction, and vibration is given in a direction to mutually shift the adhered surfaces 2a and 2a. In this way, it is possible to bond the first and second honeycomb segments 2 and 2 together.
Next, a third porous honeycomb segment 2, in which a foundation layer is formed on one adhered surface 2a and an adhesive is further coated on the foundation layer, is disposed closely so as to allow the adhered surface 2a thereof and another adhered surface 2a of the first honeycomb segment 2 to face each other while interposing the adhesive therebetween (see FIG. 2B) In this state, it is possible to bond the third honeycomb segment 2 to the first honeycomb segment 2 as similar to the second honeycomb segment 2.
Moreover, a fourth porous honeycomb layer 2, in which a foundation layer is formed on two adhered surfaces 2a and 2a and an adhesive is further coated on the foundation layer, is disposed closely between the second and third honeycomb segments 2 and 2 (see FIG. 2C). In this state, it is possible to bond the fourth honeycomb segment 2 to both the second and third honeycomb segments 2 and 2 as similar to the second and third honeycomb segments 2.
Furthermore, a fifth porous honeycomb layer 2, in which a foundation layer is formed on one adhered surface 2a and an adhesive is further coated on the foundation layer, is disposed closely so as to allow another adhered surface 2a of the second honeycomb segment 2 and the adhered surface 2a thereof to face each other while interposing the adhesive therebetween (see FIG. 2D). In this state, it is possible to bond the fifth honeycomb segment 2 to the second honeycomb segment 2 as similar to the foregoing process.
Subsequently, respective honeycomb segments 2 are sequentially bonded likewise by giving pressure and vibration every time. Lastly, a sixteenth porous honeycomb segment 2, in which a foundation layer is formed on two adhered surfaces 2a and 2a and an adhesive is further coated on the foundation layer, is bonded while giving pressure and vibration, whereby the bonding process for the ceramic honeycomb structure 100 can be completed (see FIG. 2E).
However, the conventional bonding method is configured to bond the respective porous honeycomb segments 2 sequentially while giving pressure and vibration every time. Accordingly, the vibration and the pressure are transmitted to the lower segments in the earlier stacking order (the segments located around the above-described first porous honeycomb segment 2) until completion of bonding of the last honeycomb segment (which is the sixteenth porous honeycomb segment 2 in the above-described example). The transmitted force acts as a separating force against the honeycomb segments 2 and 2 which are bonded to each other. Accordingly, the method has a problem that the adhesive layers 3 for bonding the lower honeycomb segments are separated, thereby causing partial deterioration of adhesive strength.
Accordingly, an object of this invention is to provide a bonding method of a ceramic honeycomb structure, which is capable of maintaining adhesive layers for bonding respective porous honeycomb segments in an original state of stacking irrespective of the order of stacking the respective honeycomb segments, and thereby bonding the whole honeycomb segments uniformly at desired adhesive strength.